Biostar TA990FXE with AMD FX-6100 appears to be auto over clocking

Hi. In August I built a PC using a second hand Biostar TA990FXE "Extreme Edition" motherboard and AMD FX-6100 six core CPU @3.3 GHz at the core of it. I recently installed the Oracle Virtualbox VM on Windows 10 and tried running a couple of Linux and BSD OS instances, during which I noticed that task manager was reporting (at times) the CPU clocking at up to 3.87 GHz (or ~17% over the quoted maximum). Note that over clocking options were disabled in the BIOS at the time. I am just curious as to whether this is due to the VM using hardware virtualisation and some feature of the CPU or motherboard detecting this and increasing the clock speed limit. Has anyone seen this kind of behaviour on your own systems?